The paper-making art has long sought to add dispersions of glass fibers to dispersions of wood pulp for the purpose of increasing the strength of the resulting paper. Glass fibers are made in generally continuous lengths and are chopped at various lengths, usually 1/4 inch to 2 inches for such applications. Dispersions of these relatively long length glass fibers greatly increase the strength of wood pulp paper. It is known that wood pulp fibers once dispersed throughout the glass fibers, help hold the glass fibers in suspension so that this combination has been looked upon by the art as having great merit, if it could be made at a near neutral pH.
Prior to the development in our previous application Ser. No. 105,713, now U.S. Pat. No. 3,749,638 there had been no way that textile glass fibers made of E-glass could be dispersed at a pH greater than approximately 2.9. Such dispersions have been too acidic for paper-making machinery which are made principally of copper-bearing materials. In our previous work we found that dispersions of E-glass fibers could be produced at pH's greater than 2.9 providing that clay or sodium metaphosphate was present in the dispersing media. This discovery, therefore, made papers formed by the mixture of pulp and glass fibers a commercial possibility. It also made it possible to produce papers made completely from glass fibers, since the paper dispersions themselves could be produced at a pH greater than 3.5.
There were, however, some applications particularly where microfibers were used having diameters as defined as beta, A, AA, AAA, AAAA, and AAAAAA diameters, wherein the clays would be retained in papers made of these tiny fibers. In filter applications, for example, the pores between the fibers would be so small as to retain the clay from the slurry, and the clay particles, therefore, would partially plug up the pores of the filter produced. In still other applications, chelating agents must be added of the water that are used for making the paper slurries for the removal of ions of iron, and the sodium metaphosphate used as a suspending agent, interfers with the chelating effect that is produced with the iron ions.
An object of the present invention, therefore, is the provision of still other materials which can be used as suspending agents for glass fibers in water, which agents preferably will not be particulates or interfere with chelating agents.
Further objects and advantages will become apparent to those skilled in the art to which the invention relates from the following description of the preferred embodiments.